1. Field of the Invention
This invention broadly relates to a process for preparing aliphatic alcohols from synthesis gas and more particularly to an improved process in which a heavy metal oxide catalyst is employed to effect the hydrogenation of carbon monoxide to produce a mixture of lower aliphatic alcohols.
Lower aliphatic alcohols have been proposed as octane enhancers or as a replacement for gasoline in fueling internal combustion engines. Certain mixtures of lower aliphatic alcohols have the EPA approval for use and are currently being marketed in the United States. The lower aliphatic alcohols can be produced from domestically available non-petroleum sources and the use of these alcohols in fuel compositions can serve to lessen the nation's dependence on foreign sources of crude oil and petroleum products.
Hydrogen and carbon monoxide, or synthesis gas, a mixture of hydrogen and carbon monoxide, can be reacted to form a mixture of lower aliphatic alcohols. The synthesis gas feedstream can be produced from such non-petroleum sources as coal and biomass in well known partial oxidation reactions.
Numerous catalytic processes have been studied in attempts to provide a viable process for the production of aliphatic alcohols from synthesis gas. The early efforts were primarily directed to the production of methanol. More recently, attention has been directed to the production of higher aliphatic alcohols or a mixture of higher aliphatic alcohols with methanol. Such a mixture is highly suitable as an octane enhancing component for motor fuel and as a substitute for tetraalkyl lead additives in motor fuel.
A major problem with the synthesis gas to alcohol conversion process is the occurrence of competing reactions constantly taking place on the surface of the catalyst. Thus, even when the desired product is formed on the catalyst, some of this product may undergo further reactions with adverse effects on the yield of the desired product. It is evident that if some means could be provided for reducing or minimizing competing reactions on the catalyst surface, then improved yields of the desired product might be obtained. In accordance with this invention, a decrease in the number of surface acid sites is achieved by treatment with a thermally stable base or derivative thereof. This procedure reduces the dehydration of product alcohols on the catalyst's acid sites and this results in improved selectivity.
2. Disclosure Statement
U.S. Pat. No. 3,345,427 discloses a dehydrogenation catalyst and process in which the catalyst consists of nickel, molybdenum and alkaline metal oxides on an alumina support.
U.S. Pat. No. 4,096,164 discloses a process for reacting hydrogen and carbon monoxide in the presence of a solid catalyst comprising rhodium with molybdenum or tungsten to produce 2 carbon-atom oxygenated hydrocarbons in which ethanol is the major component.
U.S. Pat. No. 4,243,553 and U.S. Pat. No. 4,243,554 disclose a molybdenum disulfide catalyst that is useful in the water gas shift, methanation, hydrogenation and dehydrogenation processes. U.S. Pat. No. 4,607,056 and U.S. Pat. No. 4,607,055 disclose synthesis gas to alcohol processes in which the catalyst comprises molybdenum in combination with a metal from the group consisting of cobalt, iron and nickel in an oxide form with an alkali metal promoter.
EPA No. 0119609 discloses an alkali promoted molybdenum disulfide catalyst that is useful for producing aliphatic alcohols from synthesis gas. The disclosures of U.S. Pat. No. 3,345,427, U.S. Pat. No. 4,096,164, U.S. Pat. No. 4,243,553, U.S. Pat. No. 4,243,554, U.S. Pat. No. 4,607,056, U.S. Pat. No. 4,607,055 and EPA No. 0119609 are incorporated herein by reference.